When approaching investors prior to filming, Six did not mention the mouth-to-anus aspect of the plot, fearing it would put off potential backers. The financiers of The Human Centipede did not discover the full nature of the film until it was complete. The film received generally mixed reviews from mainstream film critics, but it won several accolades at international film festivals. The film was released in the United States on a limited theatrical release on 30 April 2010. A sequel, entitled Full Sequence, also written and directed by Six, was released in 2011.

Lindsay (Ashley C. Williams) and Jenny (Ashlynn Yennie), two American tourists in Germany, are drugged and involuntarily detained by crazed surgeon Dr. Josef Heiter (Dieter Laser) when they seek help at his house after they get a flat tire. The women awake in a makeshift medical ward. They witness Heiter kill a kidnapped truck driver after Heiter informs him he is "not a match". Heiter secures a new male captive, Japanese tourist Katsuro (Akihiro Kitamura). The doctor explains that he is a world-renowned expert at separating Siamese twins, but dreams of making new creatures by sewing people together. He describes in detail how he will surgically connect his three victims mouth-to-anus, so that they share a single digestive system.

After Lindsay tries to escape and fails, Heiter explains that he had previously experimented with creating what he called a "three-dog", also joined mouth-to-anus. However, the three-dog died shortly after surgery. Heiter tells Lindsay that one dog tried to escape and that dog became the middle, thus this caused the most pain to the dog and as punishment for her escape attempt, she will become the middle part of his centipede. Heiter performs the surgery, placing Katsuro at the lead, Lindsay in the middle and Jenny at the rear. He removes the front teeth of both women and mutilates the buttocks of both Katsuro and Lindsay in order to provide easier access to the rectums, to which he hideously stitches and grafts their mouths. During his procedure, he severs the ligaments within his victims' knees to prevent leg extension, forcing his victims to crawl. He then connects his victims together in a straight line with their mouths surgically attached to the anus of the victim in front of them.

Once the operation is complete, Heiter attempts to train his centipede as a pet, often belittling Katsuro with racist insults and beating him with a crop when he becomes rebellious. When Katsuro defecates, Lindsay is forced to swallow his excrement while the doctor watches in delight. However, he eventually becomes irritated after being kept awake by the constant screaming of Katsuro (who, as the front part of the centipede, has his mouth free and is still able to speak) and the realization that Jenny is dying from septicemia. When two detectives, Kranz (Andreas Leupold) and Voller (Peter Blankenstein), visit the house to investigate the disappearance of tourists, Heiter comes up with an idea to add them as replacements for Jenny in a new creation; a four-segment centipede. He offers the two detectives water spiked with sedatives in hopes of knocking the two unconscious. After being given the water, the detectives become suspicious and obtain a search warrant for his home. While the detectives leave Heiter's home, the victims attempt to escape. Katsuro attacks Heiter in the process. Their attempt to escape ultimately fails. Katsuro confesses to the doctor that he deserves his fate because he had treated his own family poorly, then commits suicide by slitting his throat with a glass shard.

Upon returning to Heiter's home, the detectives forcefully conduct separate searches as an injured Heiter hides near his swimming pool. Kranz finds the ward along with Heiter's victims. Voller begins to feel ill from the earlier drugging, and Heiter stabs him with the scalpel pulled from his leg during Katsuro's attack. Upon finding Voller dead, Kranz is shot by Heiter with Voller's sidearm. Kranz responds by shooting Heiter in the head before dying. Back in the house, Jenny and Lindsay hold hands as Jenny dies. Lindsay sobs as she is left alone in the house, trapped between her deceased fellow captives. Her fate is left unknown. The film ends with the sounds of her sobbing while the camera pans to the roof of the house.

Dieter Laser as Dr Josef Heiter, a retired surgeon[3] who specialised in the separation of conjoined twins, but in retirement is more interested in joining creatures together. Casting for the role of Heiter took place in Berlin, and Six intended to cast Laser before he had even read for the part, after Six saw a DVD of one of Laser's previous films.[4] Laser had previously appeared in over 60 mostly German-language films,[5] including Der Unhold and Baltic Storm.[6] Upon meeting him in Berlin, Six gave Laser a shot-by-shot explanation of Heiter's scenes, and Laser, impressed by Six's dedication and passion, agreed to take part in the film.[7] Laser contributed considerably to the development of Heiter's character. For example, because Heiter views the "centipede" as his pet, Laser felt that it was important that Heiter appeared naked during a scene in which he swam in full view of his victims, because Laser said "you aren't ashamed to be naked"[8] around a pet.

Ashley C. Williams as Lindsay, an American tourist and the central section of the centipede. Auditioning for the roles of Jenny and Lindsay took place in New York City.[9] Six said during the auditioning process, many actresses walked out of readings in disgust after hearing the full nature of the role.[10] Others thought they would be able to take on the role, but found it was "too much"[11] for them once they got onto their hands and knees behind another actor. Williams expressed concerns about the nudity expected of her in the film, but took the role when she was assured it would be modest and of a non-sexual nature.[9]

Ashlynn Yennie as Jenny, the rear section of the centipede. As with Williams, The Human Centipede was Yennie's first major film role.[12] Yennie was one of several actresses to audition for the role, as the producers searched for an actress who would have good on-screen chemistry with Williams.[9] Yennie was able to further develop her relationship with Williams when the pair shared an apartment in the Netherlands during filming.[13] Yennie auditioned to Ilona Six, sister of Tom Six and the film's producer,[6] and did not meet Tom Six, who had viewed tapes of her reading, until fitting for the centipede special effects in the Netherlands.[12] Yennie was drawn to the role by the humanity throughout the story, referring to how the three victims of Heiter are unwillingly forced into their situation. She also said the story was so realistic it scared her.[14]

Akihiro Kitamura as Katsuro, a Japanese tourist and front section of the centipede. Having already acted in or written for a number of films and television shows (including popular American television series Heroes),[6] Kitamura was a relatively experienced actor compared to other cast members. He auditioned for the role of Katsuro via Skype from Los Angeles after the casting director saw him on television and recommended him for the role.[15] The rest of the cast did not meet Kitamura until the day before shooting commenced.[9]

Rene de Wit as Truck Driver, one of Heiter's victims. De Wit had previously worked with Six in his 2008 film I Love Dries.[16]

The inspiration for the film's plot came from a joke that writer/director Tom Six once made to his friends about punishing a child molester they saw on TV by stitching his mouth to the anus of an overweight truck driver.[7] Six saw this as the concept for a great horror film, and he began to develop the idea.[17] He has said he was heavily influenced as a filmmaker by the early works of David Cronenberg and Japanese horror films.[18] Six has said he prefers horror films that are more realistic over "unbelievable"[11] monster films, and said that he gets "a rash from too much political correctness."[19] Major influences for The Human Centipede were Pier Paolo Pasolini's controversial 1975 Italian drama film Salò, or the 120 Days of Sodom, which was notable for its scenes depicting intensely graphic violence, sadism, and sexual depravity, as was the work of Japanese director Takashi Miike.[20] Six has also expressed his love of the works of David Lynch.[21] Further inspiration came from Six's previous work as a director on the Dutch series of Big Brother, where he had been able to observe people who "did crazy things when they were alone and thought they were not (being) watched."[22]

Six has stated that The Human Centipede is, to an extent, a reflection on fascism. Dieter Laser, who played the antagonist Dr Heiter, said during the promotion of the film that he felt the guilt of Nazi actions during the war had haunted ordinary Germans for generations, and that as a German whose father participated in the war, he often felt "like a child whose father is in jail for murder."[23] The inclusion of a German villain came from this, with Six citing both the German invasion of the Netherlands during World War II and the Nazi medical experiments as inspiration.[24] Laser stated in an interview with Clark Collis for Entertainment Weekly that he considered the film a "grotesque [parody] about the Nazi psyche".[7] Heiter's name was an amalgamation of several Nazi war criminals, his surname (literally meaning "cheerful" in German) a combination of the names of Nazi doctors Fetter and Richter, and his first name coming from Josef Mengele, who carried out experiments on prisoners at Auschwitz concentration camp.[25] World War II also played an influence on the nationality of the other main characters who were American and Japanese.[26] Six includes many horror film clichés in the first act, such as a broken-down car, lack of phone signal[27] and very naïve victims.[11] Six did this in an attempt to lull audiences into thinking they are watching a conventional horror film, therefore making Dr Heiter's treatment of his victims more shocking.[28]

Six placed a Japanese male at the front of the centipede for two reasons: first to create a language barrier between the doctor and the centipede. Throughout the film the characters (with the exception of Heiter who for the most part speaks to the centipede in English) speak in their native languages only (subtitled for the viewer into English where necessary). Katsuro, as the front part of the centipede, can only speak Japanese and therefore cannot speak with either the doctor or Jenny and Lindsay. Secondly, Katsuro's position in the centipede sets up the opportunity for the doctor and the male victim of the centipede to fight toward the climax of the film.[29] Six stated in the director's commentary for The Human Centipede that he has a personal fear of hospitals and doctors, so he stretched out the scene where Heiter explains how he will create the centipede and the subsequent procedure to create his "own nightmare."[30]

While seeking funding for the film, Six pitched the idea of a surgeon who sewed people together.[31] He did not initially reveal that the victims would be joined mouth-to-anus, as he believed this idea would stand no chance of receiving investments.[32] His backers felt that the idea of a surgeon sewing people together was original and Six received funding.[31] However, they did not learn the exact details of the film until it had been completed.[7] Six claimed that they were very happy with the finished film.[33] Before signing on, the actors were given an outline of the storyboard rather than a complete script. They were also shown sketches of how the centipede would be formed.[9]

Although The Human Centipede is set in Germany, principal photography took place in the Netherlands due to the neighboring countries' similar landscapes.[34] Heiter's home, where most of The Human Centipede takes place, was a villa in the Netherlands found by the production team. The property was in a residential area and not surrounded by woodland as it appears in the film, but by other houses. This meant the filmmakers had some difficulty ensuring that the other houses did not appear in shot.[35] Some conversion of the property took place prior to filming, for example, a cinema room was converted to form Heiter's basement operating theatre,[36] with real hospital beds and intravenous drips rented from a local hospital.[37] The paintings of conjoined twins that were displayed throughout the house were painted by Tom Six, which he felt contributed to the atmosphere in the house.[38] The hotel room scene near the beginning of the film was filmed in a hotel suite at a location near Amsterdam.[39] The film was shot almost entirely in sequence, which Yennie stated helped the actors to develop their characters throughout the film.[12] The opening scene, which only featured Laser and de Wit, was shot on the last day of filming.[40]

Laser remained in character as Heiter throughout the filming process, often shouting at the rest of the cast on set,[15] but wherever possible staying away from the other actors and crew between scenes to preserve a level of separation.[41] He only ate food he had brought onto the set himself,[42] eating mostly fruit.[15] He contributed dialogue for his character and selected many of his character's outfits from his personal wardrobe.[43] Six claims that the jacket Heiter wore, which was bought by Laser, was a genuine jacket worn by real Nazi doctors.[44] Laser was also happy for the other actors in The Human Centipede to add their own ideas to the film. For example, when Heiter is explaining his procedure to his victims, Katsuro's dialogue was improvised, which pleased Laser.[15] During filming Laser accidentally kicked Kitamura (Katsuro), leading to a fight on set between the actors. The incident contributed to the tension and anger throughout the scene they were filming, in which Heiter sits at his dining table eating while the centipede eats dog food from the floor alongside him.[45] Laser also hurt Williams during the scene when Heiter roughly grabs and injects Lindsay, which caused a pause in shooting before the filmmakers could continue.[46]

The Nazi influence behind Heiter led to the use of classical music when the doctor is "training" his centipede. The music was deliberately played at low quality to simulate the music coming from a loudspeaker, in much the same way as music was sometimes played in Nazi concentration camps.[47] Many of the sound effects in The Human Centipede were created by manipulating meat. For example, the sound of a nose being broken was made by snapping bones within cuts of raw meat.[48] Due to the discomfort of spending long periods on their hands and knees, the actors playing the centipede were given massages at the end of each day of filming.[49] Yennie stated that she and Williams experienced jaw pain from holding a bit in their mouths during filming, but overall she did not feel that the physical side of filming had been excessively difficult.[50]

Dr Heiter attempts to "train" his completed human centipede. The use of bandages in The Human Centipede allowed the filmmakers to imply a more graphic and disturbing idea than is actually shown on screen.[51]

The Human Centipede contains relatively few gory images; little of the surgical procedure is depicted directly,[52] no excrement is shown on screen,[53] and according to Kim Newman in Empire, it is "never quite as outrageous as it threatens to be."[54] Six stated that he wanted the film to be as authentic as possible[55] and claimed to have consulted a Dutch surgeon during the creation and filming process,[7] resulting in the film being "100% medically accurate."[56] Six said that the surgeon initially wanted nothing to do with his film, as he felt Six was "crazy" and the idea had "nothing to do with medical science." However, the surgeon changed his mind and decided that he in fact liked the idea, and so came up with a method of creating a human centipede.[57] Six has claimed that the central and rear members of the centipede could survive for years by supplementing their diet with an IV drip.[11] The special effects team was led by a father and son team, Rob Hillenbrink and son Erik.[9] They designed the final composition of the centipede from sketches provided by the consulting surgeon.[58] The actors who made up the centipede wore hardened underwear, compared by Yennie to shorts,[59] which had a rubber grip for the actors to wear for the actor behind on which to bite, creating the illusion of the mouth-to-anus connection.[15] Six kept secret how the centipede would be formed as long as possible, and Yennie claimed that even her make-up artist did not know, asking Yennie what kind of "suit" the actors would be wearing.[12]

When Heiter is operating on his victims, Jenny's teeth were digitally removed in post-production.[60] However, other effects were relatively simple to create. Heiter's "three dog" was created by photoshopping an image of three Rottweilers to create an image of dogs joined together.[61]Colour grading was used extensively throughout the production of The Human Centipede. For example, at the end of the film when Lindsay is left between the dead bodies of Jenny and Katsuro, their skin tones were lightened to further emphasise that they were dead and Lindsay was still alive.[62]

The rain when Jenny and Lindsay's car breaks down was added digitally in post-production.[63] The filmmakers had not been granted permission to film at the roadside location, but went ahead against the authorities' wishes as Six felt the location in the woods was ideal for the scene.[64] When Heiter's window is repaired after Lindsay's escape attempt, the use of a tracking shot through the window pane required the reflection of the crew to be digitally removed from the glass.[65] The film contains a large number of long tracking shots;[66] Six has cited the influence of Takashi Miike who also uses many tracking shots in his films.[20]

During promotion for The Human Centipede, press materials claimed that the film was "100% medically accurate".[56] Six and the producers frequently stated that the film had been described as "the most horrific film ever made,"[67] and many writers, such as Karina Longworth of LA Weekly magazine[53] and Jay Stone of the Calgary Herald[68] described the film as torture porn. Roger Ebert, writing in the Chicago Sun-Times stated that he felt the film had been "deliberately intended to inspire incredulity, nausea and hopefully outrage."[19] However, writing in The Guardian, David Cox noted that he had been unable to trace the source of this quote as the "most horrific film ever made" and had contacted Six to attempt to ascertain the origin of this judgement.[67] Six claimed that the statement had originally been made by The Sun newspaper in the United Kingdom. However, Cox was unable to trace any article making this claim. When asked by Cox as to what Six regarded as the "most horrific" film, Six stated he in fact believed it to be Pier Paolo Pasolini's Salò, or the 120 Days of Sodom.[67]

The Human Centipede was released in the United States without an MPAA rating.[19] It was released theatrically in New York City on 30 April 2010 and had a limited release in the US shortly afterward, distributed by IFC Films.[69] Throughout 2009, the film was included in several film festivals around the world including the London FrightFest Film Festival, Leeds International Film Festival,[6]Sitges Film Festival,[70] and Screamfest Horror Film Festival.[6] Six remarked on how many film festival audiences reacted strongly to the film, sometimes almost vomiting in the cinema aisles. To Six's amusement, Spanish audiences often found the film funny, and laughed throughout screenings.[71] Six claimed that the "buzz"[72] surrounding the film led to several studios approaching him to discuss its distribution.[72] IFC Films has a history of releasing unconventional horror films, having previously distributed the Norwegian Nazi-zombie feature Dead Snow and the 2009 release Antichrist.[73]The Human Centipede's US gross was $181,467, and worldwide takings amounted to $252,207.[74]

The Human Centipede was released in the United Kingdom on DVD and Blu-ray on 4 October 2010[76] and in the US the following day,[77] where, as of September 2011, DVD sales have totalled $2,113,186.[78]

The Human Centipede received mixed reviews.[79]Review aggregator web site Rotten Tomatoes gave the film a 49% 'Rotten' rating, based upon 91 reviews, with an average rating of 5.1 out of 10; the general consensus states: "Grotesque, visceral and hard to (ahem) swallow, this surgical horror doesn't quite earn its stripes because the gross-outs overwhelm and devalue everything else."[80] At Metacritic, which assigns a weighted average score out of 100 to reviews from mainstream critics, the film received an average score of 33 based on 15 reviews.[81]

Giving the film three stars out of five, Empire writer Kim Newman stated that "underneath an extremely repulsive concept, this is a relatively conventional horror movie."[54]Variety Magazine writer Peter DeBurge criticised the film's lack of any form of social commentary, stating that it could not "be bothered to expand upon its unpleasant premise, inviting audiences to revel in its sick humor by favoring Dr. Heiter ... and characterizing the victims as shallow expendables."[82] Writing in Entertainment Weekly, Clark Collis was broadly positive about Dieter Laser's performance as the Doctor, and praised Six's direction, saying Six "has put together his nightmare yarn with Cronenbergian care and precision."[83] Collis said The Human Centipede was "without question one of the most disgusting horror films ever made."[83] Writing in The Guardian, Peter Bradshaw gave the film three out of five, saying that whilst "entirely deplorable and revolting" the film was "sort of brilliant".[3]Total Film writer Jamie Russell gave the film four stars out of five, calling it "Shocking, funny, disturbing... a throwback to the glory days of Cronenberg."[84]

Sukhdev Sandhu in The Daily Telegraph was generally negative about the film, stating, "The Human Centipede has its moments, but they're largely obscured by umpteen holes in the plot as well as by reams of exposition"[85] and that it was "an ultimately underwhelming affair that's neither sick or repellent enough to garner the cult status it so craves."[85]The New York Times review by Jeannette Catsouli noted that whether the film was "a commentary on Nazi atrocities or a literal expression of filmmaking politics, the grotesque fusion at least silences the female leads, both of whose voices could strip paint."[86] Writing in the Chicago Sun Times, Roger Ebert did not assign the film a star rating (not to be confused with awarding it zero stars), stating, "I am required to award stars to movies I review. This time, I refuse to do it. The star rating system is unsuited to this film. Is the movie good? Is it bad? Does it matter? It is what it is and occupies a world where the stars don't shine."[19]

Critics and a doctor have dismissed Six's claim that the film was "100 percent medically accurate" as "ludicrous"[55] and "rubbish".[87] Dr John Cameron, speaking to TV3 News in New Zealand gave an interview about the feasibility of a human centipede, stating how he believed it would be difficult for a join between different people to heal and form a connection, and how the centipede would quickly die from lack of nutrition.[88] John Martin, a former Hollywood film executive and CEO of Alamo Drafthouse Cinemas said Six's claims of 100 percent medical accuracy should be viewed with reference to the kind of shock gimmicks that film producers had long used to attract attention. Martin compared Six's claims to those of Kroger Babb and William Castle who had also made "grand promises" about what they were putting on screen in a bid to lure audiences.[55]

Despite mixed reviews, the film won several awards in 2009 during advance screenings at various international horror film festivals, including Best Picture/Movie at Fantastic Fest (Austin, Texas), Screamfest Horror Film Festival (Los Angeles), and the Sainte Maxime International Horror Film Festival.[6] Laser won Best Actor in the horror category at Fantastic Fest and the film won the award for Best Ensemble Cast at the South African Horrorfest Film Festival.[6]

When Tom Six began creating the Human Centipede sequels, he envisioned a trilogy that works as a "movie centipede". Each sequel opens with the ending of the previous film, as the events of that film influence said sequel. Although every film works as a standalone movie, they can all be connected to form a single 4.5 hour-long film.[89][90]

While promoting The Human Centipede, Six stated that he had started work on a sequel to First Sequence, titled The Human Centipede 2 (Full Sequence). Shooting on a similar budget to the first film,[91] Six stated the sequel would be a much more graphic and disturbing film; First Sequence being "My Little Pony compared with part two."[92] Yennie stated at the May 2010 Weekend of Horrors that the sequel would contain "the blood and shit"[93] that viewers did not see in the first film.[93] The plot of Full Sequence involved a centipede made from twelve people, featured a largely British cast and was given the tag-line "100% medically inaccurate".[94]

The plot of Full Sequence involves a man who after becoming sexually obsessed with a DVD recording of First Sequence decides to create his own human centipede. The film had been planned for a DVD release in the United Kingdom. However, upon submitting the film to the BBFC for classification, the film was rejected due to content that was "sexually violent and potentially obscene".[95] The BBFC's report criticised the film as making "little attempt to portray any of the victims in the film as anything other than objects to be brutalised, degraded and mutilated for the amusement and arousal of the central character, as well as for the pleasure of the audience"[96] and that the film was potentially in breach of the Obscene Publications Act, meaning its distribution in the UK would be illegal.[96] Bounty Films, the UK distributor, appealed the decision, and the film was eventually passed with an 18 certificate in October 2011. To achieve the 18 rating, thirty-two cuts were made from the film, removing two minutes and thirty-seven seconds from the original version.[97]

The third and final film in the trilogy, The Human Centipede 3 (Final Sequence), received a limited theatrical release on 22 May 2015. The film features the largest human centipede in the series, composed of five hundred victims,[98] as Six says "each film is a reaction to the other. And the film got so big, it was a pop culture phenomenon, and people wanted more: a bigger centipede, helicopters and things… it had to be bigger and bigger. And what I did, I used the idea and almost made a parody on the human centipede films itself."[90] As Full Sequence was intended to make First Sequence look like My Little Pony in comparison, Final Sequence was intended to make Full Sequence resemble a Disney film.[99] The movie features the tag-line "100% Politically Incorrect". Both Dieter Laser and Full Sequence star Laurence R. Harvey returned in starring, albeit different, roles.[100]

The Human Centipede (Final Sequence) was nominated for two Golden Raspberry Awards in the categories of "Worst Director" and "Worst Prequel, Remake, Rip-Off, or Sequel", respectively.[101][102] It was also named the second worst movie of 2015 by Entertainment Weekly and The A.V. Club.[103][104] In 2016, a compilation film of the entire trilogy titled The Human Centipede (Complete Sequence) was released, running a total of 275 minutes.[105][106]